A cDNA that encodes a novel Na ؉ -independent neutral amino acid transporter was isolated from FLC4 human hepatocarcinoma cells by expression cloning. When expressed in Xenopus oocytes, the encoded protein designated LAT3 (L-type amino acid transporter 3) transported neutral amino acids such as L-leucine, L-isoleucine, L-valine, and L-phenylalanine. The LAT3-mediated transport was Na ؉ -independent and inhibited by 2-aminobicyclo[2.2.1]heptane-2-carboxylic acid, consistent with the properties of system L. Distinct from already known system L transporters LAT1 and LAT2, which form heterodimeric complex with 4F2 heavy chain, LAT3 was functional by itself in Xenopus oocytes. The deduced amino acid sequence of LAT3 was identical to the gene product of POV1 reported as a prostate cancer-upregulated gene whose function was not determined, whereas it did not exhibit significant similarity to already identified transporters. The Eadie-Hofstee plots of LAT3-mediated transport were curvilinear, whereas the low affinity component is predominant at physiological plasma amino acid concentration. In addition to amino acid substrates, LAT3 recognized amino acid alcohols. The transport of L-leucine was electroneutral and mediated by a facilitated diffusion. In contrast, L-leucinol, Lvalinol, and L-phenylalaninol, which have a net positive charge induced inward currents under voltage clamp, suggesting these compounds are transported by LAT3. LAT3-mediated transport was inhibited by the pretreatment with N-ethylmaleimide, consistent with the property of system L2 originally characterized in hepatocyte primary culture. Based on the substrate selectivity, affinity, and N-ethylmaleimide sensitivity, LAT3 is proposed to be a transporter subserving system L2. LAT3 should denote a new family of organic solute transporters.

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ObjectiveOncolytic viruses (OVs) represent promising, proinflammatory cancer treatments. Here, we explored whether OV-induced innate immune responses could simultaneously inhibit HCV while suppressing hepatocellular carcinoma (HCC). Furthermore, we extended this exemplar to other models of virus-associated cancer.Design and resultsClinical grade oncolytic orthoreovirus (Reo) elicited innate immune activation within primary human liver tissue in the absence of cytotoxicity and independently of viral genome replication. As well as achieving therapy in preclinical models of HCC through the activation of innate degranulating immune cells, Reo-induced cytokine responses efficiently suppressed HCV replication both in vitro and in vivo. Furthermore, Reo-induced innate responses were also effective against models of HBV-associated HCC, as well as an alternative endogenous model of Epstein–Barr virus-associated lymphoma. Interestingly, Reo appeared superior to the majority of OVs in its ability to elicit innate inflammatory responses from primary liver tissue.ConclusionsWe propose that Reo and other select proinflammatory OV may be used in the treatment of multiple cancers associated with oncogenic virus infections, simultaneously reducing both virus-associated oncogenic drive and tumour burden. In the case of HCV-associated HCC (HCV-HCC), Reo should be considered as an alternative agent to supplement and support current HCV-HCC therapies, particularly in those countries where access to new HCV antiviral treatments may be limited.

Despite high rates of loss of heterozygosity affecting various chromosomes, the number of tumor suppressor genes (TSGs) found to be consistently involved in primary liver cancer is low. In the past decade, characterization of homozygous deletions (HDs) in tumors has become instrumental to identify new TSGs or to reveal the influence of a particular TSG on the development of a specific tumor type. We performed a detailed HD profiling at 238 critical loci on a collection of 57 hepatobiliary tumor cell lines (hepatocellular, cholangiocellular, and bile duct carcinomas, hepatoblastomas, and immortalized hepatocytes). We identified HDs at 9 independent loci, the analysis of which was extended to 17 additional hepatobiliary tumor cell lines. In total, 34 homozygous losses involving 9 distinct genes were detected in the 74 cell lines analyzed. Besides expected deletions at the p16-INK4A/p14-ARF, FHIT, AXIN1, and p53 genes, we detected HDs at the PTEN, NF2, STK11, BAX, and LRPDIT genes that were formerly not known to be implicated in human liver tumorigenesis. In conclusion, our data suggest that these genes may represent novel liver tumor suppressive targets. Additional tumorigenic pathways should be carefully considered in hepatocarcinogenesis. ( H epatocellular carcinoma (HCC), the main histologic form of primary liver cancer, is one of the most prevalent human tumors in the world. 1,2 Chronic infections of the liver by hepatitis B or hepatitis C viruses represent the dominant etiologies of HCC. 3 The historically recent spread of hepatitis C virus in human populations will result in a substantial increase in HCC incidence in developed countries and several epidemiologic surveys already have detected such a trend for the past 20 years in Japan, the United States, and Europe. 4,5 Until recently, chromosomal abnormalities occurring in HCC were defined poorly. We and others have performed allelotyping and comparative genomic hybridization studies to characterize the main chromosome targets in human liver tumorigenesis. 6-8 Only a handful of cancer genes are, however, consistently found mutated in this tumor type. p53 and AXIN1 genes are inactivated by somatic mutations in, respectively, 30% and 5% of cases, whereas p16-INK4A and SOCS1 are silenced through promoter hypermethylation in more than 50% of cases. 9-13 Finally, ␤-catenin, the only proto-oncogene previously found to be mutated in liver cancer, is activated in 20% of the samples. 14 The liver tumor-suppressive function of the product of the mannose-6-phosphate/insulinlike growth factor 2 receptor (IGF2/M6PR) gene is suspected but remains still controversial. 15,16 The past decade has seen the isolation of numerous tumor suppressor genes (TSGs) through the characterization of homozygous deletions (HDs) in primary tumors and cell lines. Although, HDs represent rare events, many of the TSG isolations, including WT1, p16-INK4A, BRCA2, FHIT, PTEN, SMAD4, and SNF5, were at least partly attributable to their detection. [17][18][19][20][21][22] In an attempt to

Lack of efficient culture systems for hepatitis C virus (HCV) has been a major obstacle in HCV research. Human liver cells grown in a three-dimensional radial-flow bioreactor were successfully infected following inoculation with plasma from an HCV carrier. Subsequent detection of increased HCV RNA suggested viral replication. Furthermore, transfection of HCV RNA transcribed from full-length cDNA also resulted in the production and release of HCV virions into supernatant. Infectivity was shown by successful secondary passage to a new culture. Introduction of mutations in RNA helicase and polymerase regions of HCV cDNA abolished virus replication, indicating that reverse genetics of this system is possible. The ability to replicate and detect the extracellular release of HCV might provide clues with regard to the persistent nature of HCV infection. It will also accelerate research into the pathogenicity of HCV, as well as the development of prophylactic agents and new therapy.